摘要:

AbstractA spatial-averaged model of boiling flow in an electrically heated vertical pipe is used to investigate and explain experimental data of various labroatories. The agreement with data is good over a variety of conditions ranging in pressure from atmospheric to 1000 psia, and in heated length from 2 to 16 ft.Two slip-ratio correlations are compared in testing the model against the stability data; the correlation of Bankoff being less successful at low subcooling than the modified Bankoff correlation due to Jones. A value of Bankoff'sKrecommended by Kholodovski is also compared for Spigt's experiment.The crucial boiling length, where the system is least stable, is used to demonstrate the dependence of stability on heating rate, flow rate, and degree of subcooling. In particular, it is shown that with the Bankoff-Jones slip ratio, an increase in the ratio of heating rate to flow rate invariably leads to less stable conditions. On the other hand, an increase in subcooling leads to less stable conditions only when the degree of subcooling is less than that at the crucial boiling length.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28945

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe solubility of hydrogen in liquid alkali metals useful as nuclear reactor coolants varies significantly with pressure and temperature. The solubility of hydrogen in eutectic sodium-potassium mixture (NaK-78) was determined at six temperatures from 300 to 704°C and at pressures below one atmosphere. For unsaturated solutions, the solubility depended on the square root of the hydrogen pressure and varied only slightly with temperature. At temperatures of 300 to 400°C, enough hydrogen could be dissolved at pressures below one atmosphere to result in precipitation of a metal hydride. Precipitation-decomposition pressures were consistent with the literature. The addition to NaK-78 of 1 to 4 at.% lithium considerably diminished the hydrogen activity and resulted in precipitation at lower hydrogen pressure. A mass action model is postulated to explain the phenomena. It is suggested that in liquid-alkali-metal mixtures, dissolved hydrogen exists largely in the form of undissociated metal-hydride molecules or ion pairs, with the different metals combining with the hydrogen in proportion to their concentration and their affinity for hydrogen.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28946

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA process is described wherein beryllium is extracted from sulfuric acid leaches by monohexadecylphosphoric acid in kerosene, and is subsequently stripped by moderately concentrated (9M) sulfuric acid. Because of its low solubility at this acid concentration, beryllium sulfate precipitates during stripping. Aluminum, the major contaminant in the leach, tends to be extracted somewhat less strongly, and because of its higher solubility in the strip solution reaches a steady-state level in the system. Testing Of the proposed process through several cycles with recycle of both organic and strip solutions produced products containing an Al:Be weight ratio of about 0.1:1. Further reduction of the aluminum content of the solid can be accomplished by repulping with sulfuric acid of slightly lower concentration.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28947

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA solvent extraction process is described for the preparation of very high-purity beryllium compounds. The process involves extraction of beryllium from an aqueous solution containing sufficient ethylenediaminetetra-acetic acid (EDTA) to complex all extractable impurities. The extractant used is a kerosene solution of 2-ethylhexoic acid. Further purification is accomplished by scrubbing the organic phase with 4-M sulfuric acid. The purified beryllium can be removed either with strong aqueous HCl or HF.Fifteen pounds of beryllium sulfate tetrahydrate, to which various impurities were added, were treated by this process in three batches, and converted to ammonium beryllium fluoride of high purity. Analyses of these products are given.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28948

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA sevenfold integral expression is derived for the absorbed dose rate from the uncollided flux of gamma rays at the center of a spherical shell shield bombarded by an omnidirectional flux spectrum of protons. The general formulation is reduced to a fourfold integral on the basis of simplifying assumptions. This simpler formulation assumes that the gamma rays are produced isotropically by an isotropic proton flux, that protons penetrating the shell are not deflected from their original direction of incidence, that the spectrum and yield of photons are independent of proton bombarding energy, and that both the incident proton spectrum and the range-energy relation for protons in matter have power-law representations.A sixfold intergral expression is derived for the absorbed dose rate from the once-collided flux of gamma rays at the center of a spherical shell shield bombarded by an isotropic flux spectrum of protons. The once-collided differential (in energy) flux of photons at the shell center is given by a fivefold integral expression.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28949

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractThe total neutron cross section of113Cd has been measured in the energy range from 0.025 to 1 eV with a crystal spectrometer using the Be(101) and NaCl(200) crystal planes as monochromators. A new method for second-order correction was applied, and the resonance at 0.181 eV was fitted to a Breit-Wigner single-level formula by the method of least squares. The resonance parameters obtained from the analysis areE0= 0.181±0.003 eV,σ0= 7847±187 b,Γ= 0.1087±0.0033 eV, andΓn= (0.0791±0.0032)×10-3eV assuming that the statistical weighing factor isg= 3/4.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28950

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA method is proposed for solving the transport equation, in which the angular dependence is treated by expansion in specially tailored trial functions. The working equations of the method are derived and simple numerical examples presented.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28951

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractMuch theoretical work has been done in the past to represent the angular dependence in the scattering source term of the Boltzmann equation by means of Legendre or other series expansions. However, relatively little work has been done to feed this information into our present-daySNcodes. TheSNtransport codes at LASL allow a representation of anisotropy in the scattering source term by means of multi-table cross-section sets and two formalisms are given here to generate these sets. Both involve the expansion of scattering cross sections in a series of Legendre polynomials, and incorporation of the expansion coefficients in the tables of transfer cross sections. One, called a consistentPapproximation, involves a simple truncation of the series; while the other, called an extended transport approximation, includes an attempt to approximate the next higher term in the series. A general expression is derived for the error in the neutron flux due to either approximation. The numerical evaluation ofSNcross-section entries for these formalisms has been computerized.Convergence with respect to Number of Tables is numerically investigated for several different neutron-transport problems: a) deep penetration of high-energy neutrons in air; b) critical size of an enriched-uranium bare sphere; c) reflector savings for an enriched-uranium sphere immersed in H2O; and d) fast-reactor core mockup on ANL's ZPR-III.It is concluded from these problems that both approximations converge rapidly with increasing number of tables and that the simple transport approximation gives quite accurate results for a wide range of problems.

ISSN:0029-5639    

DOI:10.13182/NSE67-2

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractProperties of the random noise source, which gives rise to inherent statistical fluctuations in nuclear reactors, have been studied under the assumption that the macrostochastic variables characterizing the state of the nuclear system follow the Markoffian random process. It has been found that the fundamental assumption leads to unified interpretation of phenomenological statements used repeatedly in the previous reactor-noise theory. They are: 1) the Langevin technique is to be applied; 2) the noise source is assumed to be white; 3) the Schottky formula is to be applied to determine the noise spectral density. Furthermore, the importance of the so-called Nyquist theorem is pointed out for establishing the Langevin method.The theorem shows that a generalized Einstein relation holds between the spectral density of the white-noise source and the linear constant operator describing the probable or expected kinetic behavior of nuclear systems. With the use of the relation, the noise spectral density has been classified into the binary and the single component. The latter comes from the fact that various nuclear reactions are of Poissonian nature, and produce the direct correlation term in the neutron field. The term is eliminated in the cross correlation function of the outputs of two detectors. The binary noise component, which comes from the branching processes and contributes to the count-rate fluctuations both for the one- and two-detector system of measurements, contains, however, the covariance of fluctuations of macrostochastic variables as unknowns. The complete determination of the noise source is accomplished with the use of the Smoluchowski consistency condition. The result offers a generalized Schottky formula.As an application, the space- and energy-dependent neutronic noise theory is treated in detail. Delayed neutrons are included from the outset. Applicability of the present theory to a slightly nonlinear system is suggested.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28953

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor

摘要:

AbstractA general transport-theory formulation of lattice kinetics is obtained by studying an infinite lattice with a macroscopic spatial-flux variation of the form exp(i B·r). A study is first made of the variation of the asymptotic inverse period and of the flux distribution as a function of the buckling vector, these being, respectively, the eigenvalue and the eigenfunction of the balance equation for the nonstationary system. This allows one to define the parameters which characterize the anisotropic migration of neutrons in the lattice. One also sees in the process that the introduction of a macroscopic curvature not only introduces net leakage,. but also modifies the mean disappearance probability from the net effect of production and absorption.The finite-medium kinetic parameters which follow are defined in terms of the corresponding zero-buckling parameters and of the buckling-dependent part of the inverse period. All the parameters are expressed in terms of integrals of periodic functions only over a unit cell instead of over the whole pile. In particular, for homogeneous systems, the volume integral drops out.In the context of the formulation of this paper, the following known facts are restressed. First, there exists a choice in defining multiplication factors, which depends on whether the production operator employed is characteristic of instantaneous production rates or of production rates in stationary systems. Second, and added to this, there is a further arbitrariness in the definition of parameters such as mean lifetimes and multiplication factors, which stems from the freedom one has in the choice of weight functions. This arbitrariness is characteristic of all parameters that are not eigenvalues. However, with a proper choice of weight functions, the multiplication factors can be made identical to the eigenvalues of static-theory balance equations. These eigenvalues have the unambiguous meaning of being the reciprocals of the factors by whichvis uniformly changed in order to stabilize nonstationary systems.Apart from its application to nonstationary systems around the critical point, the study is also applicable to pulsed systems which may be multiplying or non-multiplying. An extension to exponential experiments on nondiverging infinite lattices can be very easily obtained.

ISSN:0029-5639    

DOI:10.13182/NSE67-A28954

出版商:Taylor&Francis    

年代:1967

数据来源: Taylor